GEM: Guided Expectation-Maximization for Behavior-Normalized Candidate Action Selection in Offline RL
- URL: http://arxiv.org/abs/2603.23232v1
- Date: Tue, 24 Mar 2026 14:04:43 GMT
- Title: GEM: Guided Expectation-Maximization for Behavior-Normalized Candidate Action Selection in Offline RL
- Abstract summary: We introduce GEM (Guided Expectation-Maximization), an analytical framework that makes action selection both multimodal and controllable.<n>During inference, GEM performs candidate-based selection using a conservative ensemble lower-confidence bound together with behavior-normalized support.<n> Empirically, GEM is competitive across D4RL benchmarks, and offers a simple inference-time budget knob (candidate count) that trades compute for decision quality without retraining.
- Score: 7.213487945222728
- License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
- Abstract: Offline reinforcement learning (RL) can fit strong value functions from fixed datasets, yet reliable deployment still hinges on the action selection interface used to query them. When the dataset induces a branched or multimodal action landscape, unimodal policy extraction can blur competing hypotheses and yield "in-between" actions that are weakly supported by data, making decisions brittle even with a strong critic. We introduce GEM (Guided Expectation-Maximization), an analytical framework that makes action selection both multimodal and explicitly controllable. GEM trains a Gaussian Mixture Model (GMM) actor via critic-guided, advantage-weighted EM-style updates that preserve distinct components while shifting probability mass toward high-value regions, and learns a tractable GMM behavior model to quantify support. During inference, GEM performs candidate-based selection: it generates a parallel candidate set and reranks actions using a conservative ensemble lower-confidence bound together with behavior-normalized support, where the behavior log-likelihood is standardized within each state's candidate set to yield stable, comparable control across states and candidate budgets. Empirically, GEM is competitive across D4RL benchmarks, and offers a simple inference-time budget knob (candidate count) that trades compute for decision quality without retraining.
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